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><DIV
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><H1
><A
NAME="LIBPQ"
></A
>Chapter 31. <SPAN
CLASS="APPLICATION"
>libpq</SPAN
> - C Library</H1
><DIV
CLASS="TOC"
><DL
><DT
><B
>Table of Contents</B
></DT
><DT
>31.1. <A
HREF="libpq-connect.html"
>Database Connection Control Functions</A
></DT
><DT
>31.2. <A
HREF="libpq-status.html"
>Connection Status Functions</A
></DT
><DT
>31.3. <A
HREF="libpq-exec.html"
>Command Execution Functions</A
></DT
><DD
><DL
><DT
>31.3.1. <A
HREF="libpq-exec.html#LIBPQ-EXEC-MAIN"
>Main Functions</A
></DT
><DT
>31.3.2. <A
HREF="libpq-exec.html#LIBPQ-EXEC-SELECT-INFO"
>Retrieving Query Result Information</A
></DT
><DT
>31.3.3. <A
HREF="libpq-exec.html#LIBPQ-EXEC-NONSELECT"
>Retrieving Other Result Information</A
></DT
><DT
>31.3.4. <A
HREF="libpq-exec.html#LIBPQ-EXEC-ESCAPE-STRING"
>Escaping Strings for Inclusion in SQL Commands</A
></DT
></DL
></DD
><DT
>31.4. <A
HREF="libpq-async.html"
>Asynchronous Command Processing</A
></DT
><DT
>31.5. <A
HREF="libpq-cancel.html"
>Canceling Queries in Progress</A
></DT
><DT
>31.6. <A
HREF="libpq-fastpath.html"
>The Fast-Path Interface</A
></DT
><DT
>31.7. <A
HREF="libpq-notify.html"
>Asynchronous Notification</A
></DT
><DT
>31.8. <A
HREF="libpq-copy.html"
>Functions Associated with the <TT
CLASS="COMMAND"
>COPY</TT
> Command</A
></DT
><DD
><DL
><DT
>31.8.1. <A
HREF="libpq-copy.html#LIBPQ-COPY-SEND"
>Functions for Sending <TT
CLASS="COMMAND"
>COPY</TT
> Data</A
></DT
><DT
>31.8.2. <A
HREF="libpq-copy.html#LIBPQ-COPY-RECEIVE"
>Functions for Receiving <TT
CLASS="COMMAND"
>COPY</TT
> Data</A
></DT
><DT
>31.8.3. <A
HREF="libpq-copy.html#LIBPQ-COPY-DEPRECATED"
>Obsolete Functions for <TT
CLASS="COMMAND"
>COPY</TT
></A
></DT
></DL
></DD
><DT
>31.9. <A
HREF="libpq-control.html"
>Control Functions</A
></DT
><DT
>31.10. <A
HREF="libpq-misc.html"
>Miscellaneous Functions</A
></DT
><DT
>31.11. <A
HREF="libpq-notice-processing.html"
>Notice Processing</A
></DT
><DT
>31.12. <A
HREF="libpq-events.html"
>Event System</A
></DT
><DD
><DL
><DT
>31.12.1. <A
HREF="libpq-events.html#LIBPQ-EVENTS-TYPES"
>Event Types</A
></DT
><DT
>31.12.2. <A
HREF="libpq-events.html#LIBPQ-EVENTS-PROC"
>Event Callback Procedure</A
></DT
><DT
>31.12.3. <A
HREF="libpq-events.html#LIBPQ-EVENTS-FUNCS"
>Event Support Functions</A
></DT
><DT
>31.12.4. <A
HREF="libpq-events.html#LIBPQ-EVENTS-EXAMPLE"
>Event Example</A
></DT
></DL
></DD
><DT
>31.13. <A
HREF="libpq-envars.html"
>Environment Variables</A
></DT
><DT
>31.14. <A
HREF="libpq-pgpass.html"
>The Password File</A
></DT
><DT
>31.15. <A
HREF="libpq-pgservice.html"
>The Connection Service File</A
></DT
><DT
>31.16. <A
HREF="libpq-ldap.html"
>LDAP Lookup of Connection Parameters</A
></DT
><DT
>31.17. <A
HREF="libpq-ssl.html"
>SSL Support</A
></DT
><DD
><DL
><DT
>31.17.1. <A
HREF="libpq-ssl.html#LIBQ-SSL-CERTIFICATES"
>Client Verification of Server Certificates</A
></DT
><DT
>31.17.2. <A
HREF="libpq-ssl.html#LIBPQ-SSL-CLIENTCERT"
>Client Certificates</A
></DT
><DT
>31.17.3. <A
HREF="libpq-ssl.html#LIBPQ-SSL-PROTECTION"
>Protection Provided in Different Modes</A
></DT
><DT
>31.17.4. <A
HREF="libpq-ssl.html#LIBPQ-SSL-FILEUSAGE"
>SSL Client File Usage</A
></DT
><DT
>31.17.5. <A
HREF="libpq-ssl.html#LIBPQ-SSL-INITIALIZE"
>SSL Library Initialization</A
></DT
></DL
></DD
><DT
>31.18. <A
HREF="libpq-threading.html"
>Behavior in Threaded Programs</A
></DT
><DT
>31.19. <A
HREF="libpq-build.html"
>Building <SPAN
CLASS="APPLICATION"
>libpq</SPAN
> Programs</A
></DT
><DT
>31.20. <A
HREF="libpq-example.html"
>Example Programs</A
></DT
></DL
></DIV
><P
>  <SPAN
CLASS="APPLICATION"
>libpq</SPAN
> is the <ACRONYM
CLASS="ACRONYM"
>C</ACRONYM
>
  application programmer's interface to <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>.
  <SPAN
CLASS="APPLICATION"
>libpq</SPAN
> is a set of library functions that allow
  client programs to pass queries to the <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>
  backend server and to receive the results of these queries.
 </P
><P
>  <SPAN
CLASS="APPLICATION"
>libpq</SPAN
> is also the underlying engine for several
  other <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> application interfaces, including
  those written for C++, Perl, Python, Tcl and <SPAN
CLASS="APPLICATION"
>ECPG</SPAN
>.
  So some aspects of <SPAN
CLASS="APPLICATION"
>libpq</SPAN
>'s behavior will be
  important to you if you use one of those packages.  In particular,
  <A
HREF="libpq-envars.html"
>Section 31.13</A
>,
  <A
HREF="libpq-pgpass.html"
>Section 31.14</A
> and
  <A
HREF="libpq-ssl.html"
>Section 31.17</A
>
  describe behavior that is visible to the user of any application
  that uses <SPAN
CLASS="APPLICATION"
>libpq</SPAN
>.
 </P
><P
>  Some short programs are included at the end of this chapter (<A
HREF="libpq-example.html"
>Section 31.20</A
>) to show how
  to write programs that use <SPAN
CLASS="APPLICATION"
>libpq</SPAN
>.  There are also several
  complete examples of <SPAN
CLASS="APPLICATION"
>libpq</SPAN
> applications in the
  directory <TT
CLASS="FILENAME"
>src/test/examples</TT
> in the source code distribution.
 </P
><P
>  Client programs that use <SPAN
CLASS="APPLICATION"
>libpq</SPAN
> must
  include the header file
  <TT
CLASS="FILENAME"
>libpq-fe.h</TT
>
  and must link with the <SPAN
CLASS="APPLICATION"
>libpq</SPAN
> library.
 </P
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